What if we force people to wait before they can comment?
Delaying comments from new users would be of dubious benefit to the community (many of the worst comments on HN are not as a rule coming from fresh new accounts, and that safeguard is easily gamed), and what we'd lose in exchange is pretty clear. It hasn't been adopted here for a reason, not just out of laziness.
I think because it could kill the thread, or demotivate the OP. People reflexively rejecting my contributions would demotivate me.